Display Email Attachment Sizes In Thunderbird

Martin Brinkmann
Feb 10, 2010
Updated • Jun 19, 2016
Email, Thunderbird

Many email providers only accept email attachments up to a specific limit size-wise. The maximum size limit is different for most providers and can range from a Megabyte to 20 or 25 Megabytes, which is supported by email providers such as Yahoo Mail and Gmail.

Since limits exist, it is important to know the total size of all files attached to emails to avoid having it rejected by the provider. If the limit is exceeded, emails will bounce so that you will have to deal with the issue then and the delay that is caused by it.

Note: Some providers and emails clients support using file hosting services to overcome the limit. Gmail lets you use Google Drive to attach files of any size to emails. What happens is that links are placed in emails instead of the actual files, so that users need to download the files manually after the email arrives in the inbox.

Displaying email attachment sizes can also be helpful for users who want to reduce the size of their mailbox.

Attachment Sizes

Attachment Sizes is an add-on for the Thunderbird email client that adds size information to all attachments of emails listed by the client.

The file size is displayed next to each file so that its usually easy to determine the overall size of all attachments. The total size of all attachments is displayed when hovering the mouse cursor over the attachment area in the email client.

This does however only work when sending emails, not when the email has already been received. But the total size is not nearly as important in that case.

Attachment Sizes is compatible with all Thunderbird 3.x clients. It can be downloaded from the Mozilla Thunderbird add-on repository.

Update: The Thunderbird add-on is no longer necessary, as Thunderbird displays the size of attachments by default.

thunderbird attachment size

Thunderbird displays the size of any attachment that you add to an email directly on the screen.

It furthermore displays a total size summary on the same page, which should provide you with the necessary information you need to decide whether the email potentially exceeds the attachment limit of the email provider.

Thunderbird displays a warning if it suspects that the total size of attachments is too large suggesting to use one of the integrated file services instead.

thunderbird file size attachment

The size of attachments is also displayed in the case of received emails. This again includes sizes for each individual file, and the total size of all mail attachments.

Display Email Attachment Sizes In Thunderbird
Article Name
Display Email Attachment Sizes In Thunderbird
Find out how to display the size of file attachments that you add to emails in the Thunderbird email client to avoid bouncing messages.
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  1. sudharsan @ Technoskillonline said on February 12, 2010 at 10:10 am

    nice one …

  2. paulus said on February 10, 2010 at 9:42 pm

    Do you mean the add on called Attachment Sizes version 0.0.5 from the webadres: https://addons.mozilla.org/en-US/thunderbird/addon/878

    1. Martin said on February 10, 2010 at 9:49 pm

      Sorry link added.

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